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Conformational junctions between left‐handed DNA in (dA‐dT) 16 and contiguous B‐DNA in a supercoiled plasmid contain chemically reactive bases
Author(s) -
Nejedlý K.,
Lilley D.M.J.,
Paleček E.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)81178-3
Subject(s) - dna supercoil , dna , z dna , reactivity (psychology) , thymine , chemistry , crystallography , plasmid , insert (composites) , stereochemistry , biophysics , biochemistry , biology , materials science , dna replication , medicine , alternative medicine , pathology , composite material
Alternating adenine‐thymine sequences in supercoiled DNA may undergo a transition to the left‐handed Z‐conformation in the presence of Ni 2+ ions and high Na + concentrations [(1989) FEBS Lett. 243, 313‐317]. In this work we have studied the junctions between B‐ and Z‐conformations in a supercoiled plasmid containing a (dA‐dT) 16 insert, by means of chemical probing. We observed enhanced reactivity of bases at both ends of the alternating tract to chloro‐ and bromoacetaldehyde. The degree of chemical reactivity was found to increase with the level of negative supercoiling. Only individual bases were observed to be reactive in the B‐Z junctions, consistent with tightly localized interfacial regions.